S. Velusamy et al. / Tetrahedron Letters 47 (2006) 923–926
925
In conclusion, a novel procedure has been described for
the oxidation of primary alcohols to aldehydes. This
method can be used for the selective oxidation of pri-
mary alcohols in the presence of secondary alcoholic
groups and the catalyst 1 is recyclable without loss of
activity over three cycles.
5 mol% 1
OH
H
OH
5 mol% TEMPO
OH
O
Toluene, 100 oC
O ,
13 h
2
OH
O
Acknowledgements
50%
Scheme 2.
This work was supported by the Department of Science
and Technology (Sanction No. SR/S1/OC-092002),
New Delhi and by the Council of Scientific and Indus-
trial Research (Sanction No. 01(1804)/02/EMR-II),
New Delhi.
O
O
NH II
NH II
N
H
N
O
O
References and notes
Cu
Cu
H
H
R'
sterically hindered
O
O
N
H
NH
OH
OH
R
R
1. (a) Transition Metals for Organic Synthesis; Beller, M.,
Bolm, C., Eds.; Wiley-VCH: Weinheim, 1998; Vol. 2, pp
350–360; (b) Sheldon, R. A.; Kochi, J. K. Metal-Catalyzed
Oxidations of Organic Compounds; Academic Press: New
York, 1981; (c) Comprehensive Organic Synthesis; Trost,
B. M., Fleming, I., Ley, S. V., Eds.; Pergamon: Oxford,
1991; Vol. 7, pp 251–325; (d) Cainelli, G.; Cardillo, G.
Chromium Oxidations in Organic Chemistry; Springer:
Berlin, 1984.
R' = alkyl, aryl
a
b
RCH2OH
[CuIIL ][TEMPO]
L = SalenH4
TEMPO
[CuILH]+ [TEMPOH]
1/2O2
CuIIL
RCHO
2. (a) Punniyamurthy, T.; Velusamy, S.; Iqbal, J. Chem. Rev.
2005, 105, 2329; (b) Mallat, T.; Baiker, A. Chem. Rev.
2004, 104, 3037; (c) Stahl, S. S. Angew. Chem., Int. Ed.
2004, 43, 3400.
H2O
Scheme 3.
3. (a) Kirihara, M.; Ochiai, Y.; Takizawa, S.; Takahata, H.;
Nemoto, H. Chem. Commun. 1999, 1387; (b) Maeda, Y.;
Kakiuchi, N.; Matsumura, S.; Nishimura, T.; Kawamura,
T.; Uemura, S. J. Org. Chem. 2002, 67, 6718; (c) Reddy, S.
R.; Das, S.; Punniyamurthy, T. Tetrahedron Lett. 2004,
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pound (Scheme 3).14c Oxidation of TEMPOH to TEM-
PO by the copper(I) complex with molecular oxygen
completes the catalytic cycle.5a–d,14c
4. (a) Yamada, T.; Mukaiyama, T. Chem. Lett. 1989, 519; (b)
Iwahama, T.; Yoshino, Y.; Keitoku, T.; Sakaguchi, S.;
Ishii, Y. J. Org. Chem. 2000, 65, 6502.
For the recyclability of 1, after completion of the oxida-
tion of 4-methoxybenzyl alcohol, the reaction mixture
was treated with water (3 mL), and the organic layer,
after drying (Na2SO4) and GC analysis, was passed
through a short pad of silica gel using ethyl acetate
and hexane as eluent to afford analytically pure 4-meth-
oxybenzaldehyde in quantitative yield. Evaporation of
the aqueous layer afforded a copper complex that was
reused for the oxidation of 4-methoxybenzyl alcohol
up to three runs in the presence of fresh TEMPO and
no loss of activity was observed (Table 2).
5. (a) Marko, I. E.; Gautier, A.; Dumeunier, R.; Doda, K.;
Philippart, F.; Brown, S. M.; Urch, J. Angew. Chem., Int.
Ed. 2004, 43, 1588; (b) Pratt, R. C.; Stack, T. D. P. J. Am.
Chem. Soc. 2003, 125, 8716; (c) Chaudhuri, P.; Hess, M.;
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Reedijk, J.; Sheldon, R. A. Chem. Commun. 2003, 2414; (e)
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2004, 6, 4821.
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5396; (d) Matsushita, T.; Ebitani, K.; Kaneda, K. Chem.
Commun. 1999, 265; (e) Hinzen, B.; Lenz, R.; Ley, S. V.
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Table 2. Recycling of catalyst 1
CH2OH
CHO
OMe
5 mol% 1/O2
5 mol% TEMPO
Toluene, 100 oC
OMe
Run
Recovery (%)a
Product (%)
1
2
3
>99
>98
>96
97
96
95
a Alcohol (1 mmol), TEMPO (5 mol %) and recovered copper complex
were stirred in toluene (3 mL) at 100 °C for 9 h under atmospheric
oxygen.
8. Martin, J.; Martin, C.; Faraj, M.; Bregeault, M. Nouv. J.
Chim. 1984, 8, 141.